The present invention relates generally to shock attenuation structure useful in protective headgear (e.g., football and aviation helmets), running shoes and other shock-attenuating applications, and more particularly to such structure wherein shock attenuation is accomplished by the deformation of a series of side-by-side layers having alternating high and low compression resistances.
Various shock attenuation systems have been developed for absorbing shock. Some systems, such as the safety hat shown in U.S. Pat. No. 3,877,076, comprise permanently deformable (i.e., crushable) shock absorbing material, such as foamed polystyrene, which is very effective in attenuating shock but which is not designed to absorb repeated impacts. Other systems comprise resilient shock-absorbing material capable of absorbing repeated impact loadings. However, the use of resilient material may pose a problem in that when it is deformed during an impact, a substantial amount of energy is stored (rather than dissipated) and then released as the material rebounds or returns to its original undeformed shape. This release of energy, sometimes referred to as the "rebound effect", may be transmitted back to the item being protected (e.g., the head in the case of headgear) and result in considerable shock to the item.
Reference may be made to co-assigned U.S. Pat. Nos. 4,558,470; 4,484,364 and 4,534,068 for shock attenuation systems generally in the field of this invention. U.S. Pat. Nos. 882,686, 1,652,776 and 4,343,047 also show various types of shock attenuation apparatus which may be considered generally relevant to the present invention.